About 31% of rentals in the San Francisco metropolitan area fit a $100,000 annual household income under Zillow’s affordability measure, the real estate company found.

Zillow sets that measure at rent of no more than a third of income, or $2,500 a month for a household earning $100,000. The metro area spans San Francisco, San Mateo, Alameda, Contra Costa and Marin counties. Nationally, about 77% of rentals meet the measure.

In the San Jose metro area, Zillow’s analysis put the share at 13%, while median monthly rent from January through August was $3,539. That share may understate the options available: Zillow counted rentals priced from $2,333 to $2,500, rather than every rental below the $2,500 ceiling.

San Francisco itself was pricier than its wider metro area in August. A typical home rented for $4,680 in the city, compared with $3,410 across the metro area, Zillow data show.